Supernova shocks are believed to be the accelerators of Galactic CRs
[1]},
and magnetic fields much stronger than
the interstellar magnetic fields are required for the particle confinement and acceleration (see Section REF ).
Magnetic field amplification in the preshock region in the literature is usually attributed to the CR-driven instabilities
[2]}.
More recently, turbulent dynamo has also been invoked as a different mechanism for magnetic field amplification in the
preshock region
[3]}, [4]}, [5]}.
The upstream turbulence can be induced by the interaction between the
CR pressure gradient in the shock precursor and the upstream density inhomogeneities
[3]}, [4]}.
Density inhomogeneities
are very common in the interstellar medium as suggested by observations
[8]}, [9]}.
[10]}
took into account the effect of ion-neutral collisional damping in a partially ionized medium
and reexamined the turbulent dynamo in the shock precursor.
